Instagram is borrowing another feature from Snapchat, although this is one you'll definitely appreciate if you value your privacy. The social site has confirmed to TechCrunch that it's testing a screenshot warning system for Stories. If you're in, you'll get a notice that Story creators can see the screenshots you take. You won't get an alert with each screenshot when you're the creator, but you will see that people took screenshots when looking at your viewer list.
There's no word on whether or not this will be a widely available feature. That likely depends on how the warnings affect habits. It might back away if it notices that many users stop watching, for example.
If this does roll out, however, it could encourage Story creation among those who'd otherwise hesitate to hit the record button. Stories on services like Instagram or Snapchat are alluring in part because you can share moments from your day without leaving a permanent public record. The alert system could discourage creepers from getting around that restriction to take embarrassing screenshots, and could help you spot abuse that you'd otherwise miss.